Therapeutic oxygen is commonly provided to subjects in order to treat a variety of medical conditions, including various conditions in which the subject suffers from a loss of lung capacity. Examples of medical conditions that may result in a loss of lung capacity include chronic obstructive pulmonary disease (COPD) such as asthma, emphysema, etc., as well as cystic fibrosis, lung cancer, lung injuries, and cardiovascular diseases. Pure or substantially pure oxygen may be delivered to the subject to treat the relevant condition. Inhaling the delivered therapeutic oxygen may help the subject achieve and/or maintain an adequate level of oxygen in his or her bloodstream.
Portable therapeutic oxygen has conventionally been provided in two ways. The first approach involves storing compressed oxygen gas in a pressure container and delivering the gas through a pressure regulator and through a hose, lumen, cannula or other passage to the subject's breathing orifices (e.g., nostrils). In some instances, the container may be wheeled such that the subject may be at least somewhat mobile. However, portable compressed gaseous oxygen systems suffer from various disadvantages, such as the fact that a full portable container typically lasts a relatively short period of time, and the fact that the system may be relatively heavy and obtrusive, which may limit the subject's mobility.
The second approach involves storing liquid oxygen (or “LOX”) in a portable container and delivering gaseous oxygen evaporated from the liquid oxygen to the subject through a hose, lumen, cannula or other passage to the subject's breathing orifices (e.g., nostrils). Such an apparatus for storing liquid oxygen and/or delivering evaporated gaseous oxygen may be referred to as an “LOX apparatus.” Although oxygen is typically a gas at standard atmospheric conditions, it may be maintained as a liquid at very low temperatures, which substantially reduces the volume of the oxygen, thus substantially reducing the required size of the LOX apparatus as compared to compressed gaseous oxygen systems. LOX apparatuses typically include a vacuum-insulated container with multilayer radiation insulation for storing and maintaining the LOX at a very low temperature.
As compared to compressed gaseous oxygen systems, an LOX apparatus enjoys a longer usable charge for a given size or weight. Accordingly, the LOX apparatus can be much smaller than known compressed gaseous oxygen systems and can provide the same or longer duration of useable charge, while being lighter and/or less obtrusive. However, typical existing LOX systems include a portable LOX container that must be refilled from a liquid oxygen dewars, which must be refilled or replaced regularly (e.g., once a month), typically by truck delivery.